92 lines
6.1 KiB
HTML
92 lines
6.1 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<title>Regular Expression Parser</title>
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<td width="10" height="49"> <font size="6" face="Verdana, Arial, Helvetica, sans-serif"><b> </b></font></td>
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<td width="85%" height="49"> <font size="6" face="Verdana, Arial, Helvetica, sans-serif"><b>Regular Expression Parser</b></font></td>
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<td width="112" height="49"><a href="http://spirit.sf.net"><img src="theme/spirit.gif" width="112" height="48" align="right" border="0"></a></td>
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<p><a name="regular_expression_parser"></a>Regular expressions are a form of pattern-matching
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that are often used in text processing. Many users will be familiar with the
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usage of regular expressions. Initially there were the Unix utilities grep,
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sed and awk, and the programming language perl, each of which make extensive
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use of regular expressions. Today the usage of such regular expressions is integrated
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in many more available systems.</p>
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<p>During parser construction it is often useful to have the power of regular
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expressions available. The Regular Expression Parser was introduced, to make
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the use of regular expressions accessible for Spirit parser construction.</p>
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<p>The Regular Expression Parser <tt>rxstrlit</tt> has a single template type
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parameter: an iterator type. Internally, <tt>rxstrlit</tt> holds the Boost Regex
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object containing the provided regular expression. The <tt>rxstrlit</tt> attempts
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to match the current input stream with this regular expression. The template
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type parameter defaults to <tt>char const<span class="operators">*</span></tt>.
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<tt>rxstrlit</tt> has two constructors. The first accepts a null-terminated
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character pointer. This constructor may be used to build <tt>rxstrlit's</tt>
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from quoted regular expression literals. The second constructor takes in a first/last
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iterator pair. The function generator version is <tt>regex_p</tt>. </p>
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<p>Here are some examples:</p>
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<pre><code><span class=comment> </span><span class=identifier>rxstrlit</span><span class=special><>(</span><span class=string>"Hello[[:space:]]+[W|w]orld"</span><span class=special>)
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</span><span class=identifier>regex_p</span><span class=special>(</span><span class=string>"Hello[[:space:]]+[W|w]orld"</span><span class=special>)
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</span><span class=identifier>std</span><span class=special>::</span><span class=identifier>string </span><span class=identifier>msg</span><span class=special>(</span><span class=string>"Hello[[:space:]]+[W|w]orld"</span><span class=special>);
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rx</span><span class=identifier>strlit</span><span class=special><>(</span><span class=identifier>msg</span><span class=special>.</span><span class=identifier>begin</span><span class=special>(), </span><span class=identifier>msg</span><span class=special>.</span><span class=identifier>end</span><span class=special>());</span></code></pre>
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<p>The generated parser object acts at the character level, thus an eventually
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given skip parser is not used during the attempt to match the regular expression
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(see <a href="faq.html#scanner_business">The Scanner Business</a>).</p>
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<p>The Regular Expression Parser is implemented by the help of the <a href="http://www.boost.org/libs/regex/index.html">Boost
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Regex++ library</a>, so you have to have some limitations in mind. </p>
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<blockquote>
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<p><img src="theme/bullet.gif" width="12" height="12"> Boost libraries have
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to be installed on your computer and the Boost root directory has to be added
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to your compiler <tt>#include<...></tt> search path. You can download
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the actual version at the <a href="http://www.boost.org/">Boost web site</a>.</p>
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<p><img src="theme/bullet.gif" width="12" height="12"> The Boost Regex library
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requires the usage of bi-directional iterators. So you have to ensure this
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during the usage of the Spirit parser, which contains a Regular Expression
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Parser.</p>
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<p><img src="theme/bullet.gif" width="12" height="12"> The Boost Regex library
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is not a header only library, as Spirit is, though it provides the possibility
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to include all of the sources, if you are using it in one compilation unit
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only. Define the preprocessor constant <tt>BOOST_SPIRIT_NO_REGEX_LIB</tt> before
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including the spirit Regular Expression Parser header, if you want to include
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all the Boost Regex sources into this compilation unit. If you are using the
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Regular Expression Parser in more than one compilation unit, you should not
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define this constant and must link your application against the regex library
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as described in the related documentation.</p>
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</blockquote>
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<p> <img src="theme/lens.gif" width="15" height="16"> See <a href="../example/fundamental/regular_expression.cpp">regular_expression.cpp</a> for a compilable example. This is part of the Spirit distribution.</p>
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<table border="0">
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<tr>
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<td width="10"></td>
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<td width="30"><a href="../index.html"><img src="theme/u_arr.gif" border="0"></a></td>
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<td width="30"><a href="refactoring.html"><img src="theme/l_arr.gif" width="20" height="19" border="0"></a></td>
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</tr>
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</table>
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<br>
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<hr size="1">
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<p class="copyright">Copyright © 2001-2002 Hartmut Kaiser<br>
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<br>
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<font size="2">Use, modification and distribution is subject to the Boost Software
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License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
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http://www.boost.org/LICENSE_1_0.txt)</font></p>
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